Synergistic removal of Cr(VI) by S-nZVI and organic acids: The enhanced electron selectivity and pH-dependent promotion mechanisms

Yibo Yuan; Xipeng Wei; Hua Yin; Minghan Zhu; Haoyu Luo; Zhi Dang

doi:10.1016/j.jhazmat.2021.127240

Synergistic removal of Cr(VI) by S-nZVI and organic acids: The enhanced electron selectivity and pH-dependent promotion mechanisms

J Hazard Mater. 2022 Feb 5;423(Pt B):127240. doi: 10.1016/j.jhazmat.2021.127240. Epub 2021 Sep 16.

Authors

Yibo Yuan¹, Xipeng Wei², Hua Yin³, Minghan Zhu¹, Haoyu Luo¹, Zhi Dang¹

Affiliations

¹ Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, School of Environment and Energy, South China University of Technology, Guangzhou 510006 Guangdong, China.
² Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, School of Environment and Energy, South China University of Technology, Guangzhou 510006 Guangdong, China; Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou 510006, China.
³ Key Laboratory of Ministry of Education on Pollution Control and Ecosystem Restoration in Industry Clusters, Guangdong Provincial Key Laboratory of Solid Wastes Pollution Control and Recycling, School of Environment and Energy, South China University of Technology, Guangzhou 510006 Guangdong, China. Electronic address: huayin@scut.edu.cn.

PMID: 34844358
DOI: 10.1016/j.jhazmat.2021.127240

Abstract

The effects of organic acids on hexavalent chromium (Cr(VI)) removal by reduced iron-based materials have been extensively studied. Nevertheless, the promotion mechanism from the perspective of the electron transfer process is still unclear. Herein, sulfidated nanoscale zero-valent iron (S-nZVI) and the selected organic acids, citric acid (containing both -OH and -COOH groups) and oxalic acid (containing only -COOH groups), showed significant synergistic promotion effects in Cr(VI) removal. The FeS and FeS₂ on S-nZVI surface could enhance the Cr(VI) reduction as the reductive entity and electron conductor. Furthermore, even though the reactivity of FeS with Cr(VI) is higher than that with FeS₂, the Cr(VI) removal efficiency by FeS₂ was much higher than that by FeS with organic acids. Under neutral and alkaline conditions (pH 6.0-8.0), organic acids promoted the diffusion, adsorption and complexation of Cr(VI) on S-nZVI surface, thus enhancing the electron selectivity towards Cr(VI). However, when the solution pH changed to acidic conditions (pH 4.0), organic acids facilitated the dissolution of Fe(II) ions from S-nZVI and enhanced the electron utilization towards Cr(VI) via the fast Fe(III) reduction process. This study provided a new insight into the Cr(VI) removal, which was beneficial to understand the application boundaries of S-nZVI for Cr(VI) remediation.

Keywords: Electron selectivity; FeS(2); Hexavalent chromium; Organic acids; Sulfidated nanoscale zero-valent iron.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adsorption
Chromium / analysis
Electrons
Hydrogen-Ion Concentration
Iron*
Water Pollutants, Chemical* / analysis

Substances

Water Pollutants, Chemical
Chromium
chromium hexavalent ion
Iron